What does a squall warning indicate?

A squall warning specifically indicates the potential for dangerous wind speeds typically associated with thunderstorms, particularly when these winds can reach speeds of 34 knots (39 mph) or greater. This warning serves as a critical alert for mariners and aviators to prepare for sudden and potentially violent changes in wind conditions.

While unstable weather conditions can certainly lead to various hazards, which might overlap with squall scenarios, the essence of a squall warning focuses on the immediate and severe wind threat posed by such weather events. Thus, this is distinct from a broader description of unstable weather conditions, which may not necessarily trigger a warning related to squalls.

The other choices point to different meteorological phenomena or implications. Extended periods of strong winds may suggest a more sustained weather system but not necessarily a sudden squall. Similarly, calm weather is the opposite of what a squall warning suggests. Therefore, understanding the specific definition and implications of a squall warning in the context of sailing safety helps clarify why it directly connects to thunderstorm-associated wind speeds rather than general weather instability.